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		<td class="col0 leftalign"> « <a href="geda-gnetlist_ug-hierarchy.html" class="wikilink1" title="geda-gnetlist_ug-hierarchy.html">Hierarchy</a>  </td><td class="col1 centeralign">  <strong><a href="geda-gnetlist_ug.html" class="wikilink1" title="geda-gnetlist_ug.html">gEDA gnetlist User Guide</a></strong>     </td><td class="col2 rightalign">  <a href="geda-gnetlist_ug-implicit_pins.html" class="wikilink1" title="geda-gnetlist_ug-implicit_pins.html">Implicit pins</a> » </td>
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<h2 class="sectionedit2"><a name="slots_and_slotting" id="slots_and_slotting">Slots and slotting</a></h2>
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<p>
Some integrated circuits provide several identical and interchangeable devices in a single package.  The classic “4000” series of logic devices is a good example of this; for example, each 4001 package contains four 2-input NOR gates.  <a href="geda-gschem_ug.html" class="wikilink1" title="geda-gschem_ug.html">gschem</a> and gnetlist provide support for working with these by using <em>slots</em>.
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<p>
<p><div class="notetip">Check the “4001-1.sym” symbol in the “4000-series logic” symbol library for an example of how to use slotting and <a href="geda-gnetlist_ug-implicit_pins.html" class="wikilink1" title="geda-gnetlist_ug-implicit_pins.html">implicit pins</a>.
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<p>
Detailed information on slotting attributes can be found in the Master Attributes List.
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<p>
gnetlist uses several symbol attributes to enable slotting.  All must be present for gnetlist to process a slotted component correctly.
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<ol>
<li class="level1"><div class="li"> Every pin must have a ”<code>pinseq=</code>” attribute and a ”<code>pinnumber=</code>” attribute.</div>
</li>
<li class="level1"><div class="li"> The ”<code>numslots=</code>” attribute indicates how many slots a component has.</div>
</li>
<li class="level1"><div class="li"> There must be one ”<code>slotdef=</code>” attribute for each slot.  This contains information about the pin numbers of the pins associated with each slot.</div>
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<li class="level1"><div class="li"> A ”<code>slot=</code>” attribute attached to each component in the schematic indicates which particular slot to use.</div>
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<p>
When processing a slotted component, gnetlist first looks for a ”<code>slotdef=</code>” attribute matching the value of the ”<code>slot=</code>” attribute.  It uses the value of the ”<code>slotdef=</code>” attribute to renumber the pins for the correct slot.  It then merges the component with other components with the same “refdes”.
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<p>
<p><div class="noteimportant">gnetlist does not currently support slotting across hierarchy.  The slots in a package cannot be split between different subcircuits.
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